Polyisobuylene-asphalt composition containing hardening agent



Patented Oct. 25, 1949 POLYISOBUTYLENE-ASPHALT COMPOSI- TION CONTAININGHARDENING AGENT Robert W. Mei-icy and Victor A. Navikas, Lancaster, Pa.,assign ore to Armstrong Cork Company,

Lancaster, Pa., a corporation of Pennsylvania Serial No. 525,944

No Drawing. Application March 10, 1944,

6 Claims. 1 This application is a continuation-in-part of our co-pendingpatent application, Serial No. 430,968, filed February 14, 1942, nowabandoned.

This invention relates to compositions of matter and more particularlyto a composition of matter which is particularly suitable for useas aliner for container closures; and it comprises a composition includingpolyisobutylene, asphalt containing a hardening agent for thepolyisobutylene, and a filler; the invention further comprises a methodof preparing the composition in which the asphalt and hardening agentare blended by heating, an intimate mixture of the hardening agent andasphalt is formed by agitating the mixture, the mixture of asphalt andhardening agent is added to the polyisobutylene, the filler is thenadded, and the resulting mixture is then heated and agitated until ahomogeneous mixture is obtained; all as more fully hereinafter set forthand as claimed.

A suitable liner is a necessity in almost all types of containerclosures. These liners must be of such a nature as to withstandsuccessfully a wide variety of conditions. For example, a liner must beflexible and compressible so that a tight seal is formed between theclosure itself and the lip of the container. Further, the liner must beimpervious to liquids and gases so that the contents of the containercannot pass through the liner and attack the closure, and the materialwhich is employed as a liner should be substantially odorless andtasteless so that no detrimental effects result from the use of thematerial as a liner for closures for foods and beverages.

The most widely used lining material has been cork or cork composition.These liners possess many of the characteristics required of a liningmaterial, and because of their heretofore availability in largequantities enabled manufacturers to employ them at relatively smallcost. However, cork or cork composition mustbe stored under carefullycontrolled conditions to prevent development of mold thereon which moldprevents their use as closure lining material. Further, these particularcork or cork composition liners, in addition to being somewhatpermeable, are no longer available in as large quantities as washeretofore the case, and, therefore, the manufacturers are faced with avery serious problem in the liner field.

Certain compositions have been proposed heretofore as materials suitablefor use in container closures as liners. However, the majority of thesecompositions are unsuitable in one respect or another. For example, manyof them such as rubber, and rubber composition possess an odor and tasteand tend to oxidize over a period of time so that the sealing propertiesare undesirably reduced. Synthetic rubbers exhibit an odor and 2 taste,and other compositions which have been proposed such as faced pulpboardare not sumciently flexible or compressible to form a tight seal betweenthe container lip and the closure. Therefore, such liners are unsuitablefor use with closures which are to be employed in capping pressure foodsand beverages.

Within the past few years there has been developed a polymer ofisobutylene which is prepared by polymerizing isobutylene in thepresence of a Friedel-Crafts catalyst such as aluminum chloride, borontrifiuoride and the like at temperatures of from 0 F. to F. or lower.Polyisobutylene has been modified with various materials and has beenemployed in quite a wide variety of uses. For example, as disclosed inU. S. Patent 2,133,412 to Anderson, polyisobutylene has been modifiedwith mineral oil and paraffin wax to produce a petrolatum-like product;a polyisobutylene coumarone-indene resin composition is disclosed in theU. S. patent to Carmody 2,241,340, but this composition is too tacky foruse in closures as a lining material; chlorinated naphthalene andpolyisobutylene is disclosed in U. S. patent to Engelhardt et a1.2,248,749, but this com position is adhesive in nature and is toxic; andAnderson et a1. disclose in U. S. Patent 2,197,461 polyisobutylene andasphalt compositions, but the compositions contain an excess of asphaltand are unsuitable for use as closure lining materials because of theirtackiness, Thus, the polyisobutylene compositions of the prior art areunsuitable as closure lining material because of the fact that they areeither too soft, too brittle, or too tacky.

Attempts have been made to harden polyisobutylene compositions by usingvarious hardening agents such as polystyrene, phenol aldehyde resins andthe like, but the resulting compositions still exhibit such a degree oftackiness and incompatibility as to be unsuitable for use as closurelining materials.

We have found a composition which exhibits remarkable properties whichmake it particularly adaptable for use as a closure lining material.Broadly, our invention comprises a composition which includespolyisobutylene, asphalt, a hardening agent for the polyisobutylene, anda filler.

This particular composition is sufficiently free of tack so that thematerial does not adhere to the lip of the container even upon prolongedcontact therewith, and there is no tendency of the material to pick updirt or other impurities during the assembly of the closure.Furthermore, the material is sufiiciently flexible and compressible toallow its use as a liner for closure for pressure foods and beverages,without danger of loss of gas from the container contents.

In addition, the composition is relatively free from cold flowproperties so that excellent sea1- ing is obtained.

The composition of our invention is prepared by incorporating thehardening agent into the asphalt by heating to a temperature of aboutthe melting point of the particular hardening agent used and agitatingthe mixture in a suitable device. The hardening agent and asphalt blendis then added to the polyisobutylene and heated at an elevatedtemperature until a homogeneous mixture is obtained. The filler is thenadded and the mixture is subjected to further heat and agitation. Thisorder of mixing is necessary in order to obtain a tack-free composition.

Although various types of asphalt may be employed in the preparation ofour composition, we have found that most advantageous results areobtained when a. blown asphalt having a melting point of about 220 F. toabout 230 F. is utilized. The use of this particular asphalt results ina final composition which is exceedingly satisfactory both from thestandpoint of carbonation retention and freedom from tack, odor, andtaste. The function of the asphalt in our composition is to allowmodification of the polyisobutylene with the hardening agent and thefiller and yet result in a composition which is compatible and nontacky.Although asphalt is tacky; polyisobutylene is tacky and the modifiedpolyisobutylene compositions of the prior art are tacky, we have found,surprisingly, that a composition comprising polyisobutylene asphalt anda hardening agent may be prepared which is nontacky and may be employedas a lining material. It appears that the asphalt, being compatible withboth the polyisobutylene and the hardening agent, increases thecompatibility of the hardening agent and polyisobutylene to such adegree that a tack-free composition is obtained. However, we do notintend to limit our invention to any particular theory of operation.

The hardening agent which may be employed according to our invention maybe selected from a wide numberv of materials, for example, a rubberresin such as rubber hydrochloride or rubber chloride or non-reactivephenolic resins, polystyrene, polycoumarone, polyindene, highmeltposition. Such polymers have an average molecular weight of about100,000 to about 150,000.

Although our composition may vary as to the proportions of theindividual ingredients thereof, we have obtained particularlyadvantageous results in closure lining materials comprising about 20 toparts by weight of polyisobutylene, about 13 to 30 parts by weight ofasphalt, about 8 to 16 parts by weight of hardening agent, and filler.For these quantities, we prefer to employ about 25 to 55 parts by weightof filler though larger or smaller amounts of filler maybe used. If theamount of filler is greatly reduced, the cost of the material is undulyincreased and there may be a tendency for the material to flow and ifthe amount of filler is greatly increased, the product may not have thedesired resiliency though the quantity of filler which should be usedwill be readily apparent to one skilled in the art. When we employ amixture of hardening agent as outlined above, we prefer to employ aboutone part by weight of a hardening agent such as polystyrene, polyindene,polycoumarone. and the like to two parts by weight of phenolic resinsuch as a condensation product of a terpene, a. phenol, and formaldehydeor a condensation product of a terpene, a phenol, and acetone. When weemploy a mixture of rubber hydrochloride or rubber chloride,polystyrene, and phenolic ing point waxes, limed rosin, ester gum, andthe like, or mixtures of these materials may be used. We have obtainedparticularly advantageous results when using one or more of thefollowing resins as the hardening agent: rubber hydrochloride, rubberchloride, polystyrene, polycoumarone, polyindene, and anon-reactive,terpene-modified phenol-carbonyl resin. Excellent results have beenobtained with a hardening agent comprising polystyrene and aphenol-carbonyl resin and also with a hardening agent comprising arubber resin such as rubber hydrochloride or rubber chloride,polystyrene, and a phenolcarbonyl resin. The preferred phenolic resinsare non-reactive, terpene-modified phenolcarbonyl resins, for example, acondensation product of a terpene, a phenol, and formaldehyde; acondensation product of a terpene, a

phenol, and acetone; and the like.

As the filling material of our composition, we

may employ-mineral fillers such as talc, clay, vermiculite, asbestine.calcium silicate, magnesium silicate, and the like or vegetable fillerssuch aldehyde resin, we prefer to employ one part by weight polystyrene,two parts by weight rubber hydrochloride or rubber chloride, and twoparts by weight phenolic resin.

In the following examples, all parts are by weight:

Example 1 This specific example illustrates the most advantageouscomposition for use as a closure lining material. Sixty parts by weightof blown asphalt having a melting point between about 220 F. and about230 F. are blended by applying heat with 15 parts by weight ofpolystyrene and 30 parts by weight of a condensation product of aterpene, phenol, and formaldehyde and with 20 parts by weight of rubberhydrochloride resin. This blended mixture is cooled, broken up, and thenworked up with parts of polyisobutylene on differential speed rolls. Onehundred twentyfive parts by weight of calcium silicate, 75 parts byweight magnesium silicate, and 30 parts by weight of iron oxide are thenadded and the mixture thus formed is then heated at a temperature of200-250 F. until a homogeneous mixture is obtained.

Example 2 This specific example illustrates a highly satisfactorycomposition for use as a closure lining material. Two hundred parts byweight of blown asphalt having a melting point between about 220 F. andabout 230 F. are blended byapplying heat with 30 parts by weight ofpolystyrenegand: 50 parts by weight of a condensation product of a.terpene, phenol, and formaldehyde. Themixe Example 3 Parts by weightPolyisobutylene 100 Blown asphalt 220-230 F. M. P. 100 Polycoumarone 40Limed rosin 60 Walnut shell flour 200 Ewample 4 Parts by weightPolyisobutylene 200 Blown asphalt of Example 2 200 Zinc resinate 25Rubber hydrochloride 50 Calcium silicate 400 Example 5 Parts by weightPolyisobutylene 75 Blown asphalt of Example 2 75 Polystyrene Rubberhydrochloride 40 Flax fiber 125 The above examples are given by way ofillustration and not by limitation and the ingredients and proportionsset forth may be varied without departing from the scope of ourdiscovery.

The composition of our invention, although it has been disclosed withparticular reference to lining materials for container closures, may beemployed for other purposes such as gasket material, and the like.

The composition of our invention is flexible, compressible, impermeableto gas and liquid and is free from tack. Such a composition having suchingredients as have been set forth above is particularly adapted as alining material for use in closures for pressure foods and beverages.Liners of such composition have retained pressures up to about 150pounds per square inch without failure of the liner itself or damage tothe container contents.

. The composition may be applied to closures by several differentmethods. The compositions may be calendered or duplexed at properthicknesses to suitable backing material such as pulpboard, newsboard,and the like, which laminated materials are then applied to closures bypunchor cutting discs from the sheet of laminated material. Thecomposition may also be applied to a backing already positioned in aclosure shell by punching out lining materials of the desired diameterfrom ribbons or strips of the composition. The composition is alsocapable of being applied directly to the closure shell without anybacking material eitheras a disc or in washer form. Although thecomposition has been described as particularly adaptable for use as aliner for closures to be used with pressure foods and beverages, it mayalso be employed as a liner for screw-type closures, those which areemployed as a sealing means for containers of non-pressure foods orbeverages.

Although our invention has been described by certain specificembodiments and specific examples, the invention is not intended to belimited by the above description, but may be otherwise embodied andpracticed within the scope of the appended claims.

We claim:

1. A composition of matter comprising about 20 to 30 parts by weight oipolyisobutylene having an average molecular weight of 100,000 to160,000; about 13 to 30 parts by weight of aaphalt containing about 8 to16 parts by weight oi hardening agent for said polyisobutylene, saidhardening agent comprising about one part by weight of polystyrene andabout 2 parts by weight of a permanently fusible resinous condensationproduct of a terpene, a phenol, and acetone; and a filler.

2. A composition of matter comprising about 20 to 30 parts by weight ofpolyisobutylene having an average molecular weight of 100,000 to150,000; about 13 to 30 parts by weight of asphalt containing about 8 to16 parts by weight of a hardening agent for said polyisobutylene, saidhardening agent comprising about one part by weight of polystyreneresin, about 2 parts by weight of a permanently fusible resinouscondensation product of a terpene, a phenol, and acetone and about 2parts by weight of rubber hydrochloride; and a filler.

3. A composition of matter comprising about 20 to 30 parts by weight ofpolyisobutylene having an average molecular weight of 100,000 to150,000; about 13 to 30 parts by weight of blown asphalt having amelting point of about 220 F. to about 230 F. containingabout 8 to 16parts by weight of hardening agent for said polyisobutylene, saidhardening agent comprising about one part by weight of polystyrene andabout 2 parts by weightrof a permanently fusible resinous condensationproduct of a terpene, a phenol, and acetone; and filler.

4. A composition of matter comprising about 20 to 30 parts by weight ofpolyisobutylene having an average molecular weight of 100,000 to150,000, about 13 to 30 parts by weight of blown asphalt having amelting point of about 220 F. to about 230 F. containing about 8 to 16parts by weight of a hardening agent for said polyisobutylene, saidhardening agent comprising about one part by weight of polystyreneresin,,about 2 parts by weight of a permanently fusible resinouscondensation product of a terpene, a phenol, and acetone and about 2parts by weight of rubber hydrochloride; and filler.

' 5. A composition of matter comprising about 20 to 30 parts by weightof polyisobutylene having an average molecular weight of 100,000 to150,000; about 13 to 30 parts by weight of blown asphalt having amelting point of about 220 F. to about 230 F. containing about 8 to 16parts by weight of hardening agent for said polyisobutylene, saidhardening agent comprising about one part by weight of polystyrene andabout 2 parts by weight of a permanently fusible resinous condensationproduct of a terpene, a phenol, and acetone; and from about 25 to about55 parts by weight of filler.

6. A composition of matter comprising about 20 to 30 parts by weight ofpolyisobutylene having an average molecular weight of 100,000 to150,000, about 13 to 30 parts by weight of blown asphalt having amelting point of about 220 F. to about 230 F. containing about 8 to 16parts by weight of a hardening agent for said polyisobutylone, saidhardening agent comprising about one part by weight of polystyreneresin, about 2 parts by weight of a permanently tusible resinouscondensation product or a terpene, a phenol, and acetone and about 2parts by weight of a rubber hydrochloride; and from about 25 to about 55parts by weight of filler.

ROBERT W. MERE-KY. VICTOR A. NAVIKAB.

No references cited.

